It's a Trefor West special for low clear water and spooky fish. You can see it in his book. The idea is that it looks like a strip of dead weed on the bottom. I love it because you can see where your bait is and it straightens visibly when a fish picks up - very exciting. It also confirmed for me at least, the differences in how chub and barbel feed. I only use it when all else has failed or I am pretty certain that nothing else will do the trick - to paraphrase Nigel in Spinal Tap, where can I go once I've turned my amp up to 11?